Well... if you are going to correct someone's grammar then I need to tell you that the proper way to express what you are saying would be "because this way the pronunciation would sound better." You cannot really say "a better pronunciation" because using an indefite article in front of the word "pronunciation" is very awkward.
As used, it was perhaps a bit awkward, but obviously once can use an indefinite article with the word in a perfectly normal and appropriate way, e.g. “That is an acceptable pronunciation of the word;” “That is a pronunciation I have never heard;” “That is a better pronunciation than before;” etc. If you are simply designating one particular pronunciation, you would of course use an indefinite article.
And really, what does it matter? If we were speaking rather than writing, no one would care about the insignificant error either in the thread title or in the post to which you refer.